132 



SCIENCE. 



[Vol. XIII. No. 315 



dead mice and birds are always found, and are common in other 

 regions as well. The well-known Grotto del Cano, near Naples, 

 is the most familiar example of such accumulations of carbonic- 

 acid gas ; and visitors are frequently entertained by the asphyxia- 

 tion of a poor dog, while the guide, whose head rises above the 

 gas, is not affected by it. Death Gulch is, however, without a peer 

 as a natural bear-trap, and may well be added to the list of the 

 wonders of the Yellowstone Park. Walter H. Weed. 



U. S. Geol. Surv., Washington, Jan. 30. 



A New Method for the Microscopical Examination of Water. 



In making microscopical' examinations of potable waters, it is 

 entirely impracticable, on account of their relative purity, to pro- 

 ceed directly. Repeated examinations of random samples might 

 yield absolutely nothing, although filtration of a few cubic centi- 

 metres through a fine cloth might show that in the same water 

 there were abundant microscopic forms. 



The importance of being able to ascertain the presence of these 

 microscopic organisms, and to determine their number and species 

 in any given sample of water, is self-evident. It is important, not 

 only from a purely scientific, but also from a sanitary, point of view, 

 to know precisely what is contained in drinking-water. Again : 

 large manufacturing interests are dependent upon the purity of the 

 water supplied to them through filters or otherwise, while many 

 large towns depend upon the efficiency of filters for the purity of 

 their water-supply. A microscopical examination of the water be- 

 fore and after filtration shows very clearly the actual work which 

 the filter accomplishes, in a way that it is impossible for chemical 

 analyses to do. From a scientific and sanitary point of view, mi- 

 croscopical examinations are accordingly of great value both as a 

 means for the study of the organisms themselves, and of the influ- 

 ences of changes in the water upon their growth, life, and death, as 

 well as the counter effects produced upon the water by them. For 

 making such examinations there have been hitherto, so far as I 

 know, but two methods employed. One of these is that proposed 

 by Dr. J. D. McDonald in his " Guide to Microscopical Examina- 

 tion of Water " (J. & A. Churchill, London, 1883). In this method 

 the sample to be examined is put into a tall glass cylinder, at the 

 bottom of which is a watch-glass suspended by a platinum wire. 

 This is allowed to stand for forty-eight hours, in order that the 

 matters held in suspension may settle into the watch-glass at the 

 bottom. The upper water is then siphoned off, and the contents 

 of the watch-glass examined under the microscope. 



The other method, the origin of which I do not know, is used at 

 present by the Massachusetts State Board of Health. In this 

 method a given quantity of water is passed through a fine linen or 

 cotton cloth tied to the lower end of a funnel. After the water 

 has passed through it, the cloth is removed, and cautiously reversed 

 over the end of a glass tube, the numerous objects which have 

 been caught upon the cloth being now upon the outside. A slide 

 is then placed under the cloth, and a puff of air blown through the 

 tube. The moisture contained in the cloth collects in a drop, 

 which falls upon the slide, carrying with it theoretically the mate- 

 rials filtered out of the water. The slide is then examined under 

 the microscope, and the organisms obtained counted. Both these 

 methods are open to very serious objections, and are so crude that 

 no fair estimates of the number of organisms contained in a given 

 sample of water can be formed. In the case of the first method, 

 I have found that by no means all of the microscopic organisms 

 settle to the bottom, even when the water is left standing a much 

 longer time than forty-eight hours, as there are many which have 

 about the same specific gravity as water, and consequently do not 

 settle. This .source of error becomes greater in proportion as the 

 water to be examined becomes purer. In the case of ordinary 

 drinking-water, the sediment is very inconsiderable, although there 

 are large numbers of organisms held in suspension. Under ordi- 

 nary circumstances, water left standing in this way gives an excel- 

 lent opportunity for the organisms present to increase. Especially 

 is this the case with filtered water, where the increase is surpris- 

 ingly rapid. From this it is plain that the sediment in the watch- 

 glass does not represent what was originally in the water, but only 



^ It is convenient to designate by " microscopic " all forms of life visible only by 

 means of the microscope, exclusive of the bacteria. 



a small part of that amount plus a part of the increase which has 

 since taken place. In the second method, if the cloth be examined 

 microscopically after presumably all the microscopic organisms 

 have been removed, it will often be found that a very large number 

 are stuck in the meshes of the cloth. 



For these two methods I have substituted one which, although 

 far from perfect, gives much better results. I have now been 

 using it for four months in making microscopical examinations of 

 water for the city of Boston. 



The new method is as follows. A known quantity of water (I 

 have found 100 cubic centimetres a convenient unit) is put into a 

 funnel in the tube of which is half an inch in depth of sand (24 to 

 30 grains to the inch). The sand is held in place by a stop' 

 made of a roll of brass wire gauze, which gives free passage 

 to the water, while it holds the sand in place. Through this 

 the water is filtered, the sand holding back the microscopic forms. 

 The experiments which I have tried, to test whether all the or- 

 ganisms are removed or not, have proven conclusively the effi- 

 ciency of the sand in holding back all the microscopic organisms in 

 the water. After all the water has passed through, the stop is re- 

 moved, and one cubic centimetre of distilled water (the water 

 which has just been filtered will answer as well) is thrown into 

 the funnel by means of a pipette. This washes the sides of the 

 funnel, and carries the sand with it down into a watch-glass which 

 is held underneath to receive it. On falling into the watch-glass, 

 the grains of sand separate and sink to the bottom, leaving the 

 lighter organisms which have been caught between them mostly 

 suspended in the water. By stirring this wash-water a more even 

 distribution of the organisms is obtained, and, if any have been car- 

 ried to the bottom by the falling sand, they are liberated ; so that 

 if the wash-water be poured off, and the sand examined under the 

 microscope, it will be found that there are no more organisms 

 among it than might be expected. Some of the water standing 

 above the sand is immediately transferred to a slide containing a 

 chamber the capacity of which is one cubic millimetre. All the 

 microscopic organisms contained in this chamber are then counted 

 under the microscope, and from the result the total number of or- 

 ganisms in the original sample is computed. I have found this 

 cubic millimetre surprisingly representative of the whole mass of 

 the wash- water, as far as the numbers go, although, as would nat- 

 urally be expected, the species vary largely in different samples. 



This method, as the first which can fairly be called^ quantitative, 

 opens up a new field, having wide and practical applications. It is 

 to be hoped that microscopical examinations may hereafter take 

 their proper place alongside of bacteriological and chemical analy- 

 ses, to which they must form important adjuncts. 



A. L. Kean. 



Mass. Inst. Technol., Boston, Feb. i. 



Triple Births in the Human Race. 



I WAS much interested in the note published in Science of Feb. 8, 

 upon triple births in the human race, and I beg to direct your atten- 

 tion to a curious case to be found among the records of Middle- 

 boro [Mass..'], in which triple births occurred in two successive 

 generations of the same family. 



Elisha Vaughan married Joanna Morton, daughter of John Mor- 

 ton of Middleboro. 



Childre}i of Elisha and Joanna Vaughan. 



Hinksman b. 1708, Jan. 11. 



Mercy 1 



Sarah y b. 1711, July 12. 



Thankful ) 



Thomas b. 1714, Dec. i. 



• Hannah b. 171 7, Oct. 25. 



Children of Hinksman and Desire Vatighan. 



Hannah b. 1733, April 29. 



Elisha 1 



Abraham V ..b. 1735, June i. 



Ebenezer ) 



Abigail b. 1737, March 21. 



The town and church records in Middleboro comment upon the 

 curious reversal of the sexes in the two generations. 



Alexander Graham Bell. 



Washington, Feb. 11 



